In the vast majority of patients with hypertrophic cardiomyopathy the diagnosis can be made by M-mode echocardiography because hypertrophy is present in regions of the left ventricule through which the M-mode beam passes. In some patients with hypertrophic cardiomyopathy the hypetrophy is located in regions that the M-mode beam cannot reach but two-dimensional echocardiography can visualize.